The present invention pertains to cooling transmission fluid in a motor vehicle and, more particularly, to a transmission oil pan with an integrated transmission fluid-to-coolant heat exchanger.
In a typical transmission for a motor vehicle, transmission fluid circulates continually throughout the transmission to lubricate and cool components that rotate at relatively high speed within a transmission case. The fluid is also used to actuate various clutches and brakes in order to change gear ratios. The fluid, which is drawn by a transmission pump from an oil pan located below and secured to the transmission case, returns to the oil pan by gravity feed after circulating through the transmission. Its temperature increases in this flow path and is lowered by passing the fluid through a heat exchanger, which is usually located behind a radiator that forms a portion of an engine cooling system in which heat from an engine coolant is transferred to an air stream flowing through the radiator. Alternatively, the temperature of the fluid can be lowered by passing the fluid through a fluid-to-coolant heat exchanger located outside the transmission. The systems that support this heat exchange consume packaging space, introduce leak risks and can be inefficient, costly and cumbersome to assemble and service.
To overcome these difficulties, one proposed solution has been to integrate a heat exchanger into a transmission oil pan, such as is shown in U.S. Pat. No. 7,637,337, which is hereby incorporated by reference in its entirety. However, this arrangement is not considered to provide sufficient heat transfer for all applications. Therefore, there is a need in the art for a transmission oil pan with an integrated fluid-to-coolant heat exchanger that provides an increased heat transfer capability.